深海扇油气勘探综述

An overview of hydrocarbon exploration in deep submarine fans

深海扇是在大陆坡海底峡谷前缘,由陆源碎屑物经浊流作用通过海底峡谷搬运至洋底堆积而成的扇形或锥形沉积体,一般可分为上部扇、中部扇、下部扇等单元。深海扇的沉积作用主要受地质构造、地形地貌、海平面变化、物源区的气候等因素的控制。世界许多大河口外都发育有大型深海扇,其中最大的为孟加拉深海扇。深海扇蕴藏着丰富的油气资源。上世纪90年代以来,随着世界对能源需求的增加、陆地和浅海区油气发现难度的增大及海洋工程技术的进步,深水勘探逐渐成为热点。深海扇和相关油气藏可能成为今后几十年油气勘探开发的最前沿。目前,国际上深海扇油气勘探已取得空前成功,已有60多个国家进行了深水油气勘探,但在我国尚属新的勘探领域。南中国海可能发育诸多具良好油气勘探前景的深海扇,目前已在珠江口盆地白云凹陷深水区发现荔湾3-1气田。由于沉积成因机理和油气成藏规律的特殊性,深海扇油气勘探与陆地及浅海区的油气勘探有着显著差异。深海勘探被认为是21世纪科学、技术和环境面临的主要挑战之一,诸多理论和技术问题尚待进一步研究和解决。

Deep submarine fan, a kind of depositional bodies in shape of fan or coniform, normally develops in the front of canyons along continental slope, and is products of terrestrial clastics by turbidity current, including several parts such as upper fan, mid fan, lower fan and so on. The sedimentation of deep submarine fan is mainly controlled by geological structure, terrain, sea-level change and provenance climate. Many large rivers in the world have great submarine fans in their estuarine area, with the Bengal Fan the biggest. There are plenty of oil and gas resources in deep submarine fans. Since 1990＇ s, deep sea exploration has become very active, because of increasing demand of energy in the world, increasing exploration difficulties in land and shallower sea and significant progress in offshore engineering technology. The research of deep submarine fans and their hydrocarbon may become a leading edge of oil and gas exploration and development in the following several ten years. Currently,8 hydrocarbon exploration in deep submarine fans has made big progress in the world, with more than 60 countries involved. For China, however, it is still a frontier of hydrocarbon exploration. There may be many deep submarine fans with excellent prospectiveness of hydrocarbon exploration in South China Sea, with LW 3-1 gas field discovered in Baiyun sag, Pearl River Mouth basin. Compared with onshore and shallower water areas, deep submarine fan is quite different in hydrocarbon exploration due to its uniqueness in sedimentary process and hydrocarbon accumulation. Deep water exploration is considered one of the major challenges to science, technology and environment in the 21st century, and a number of theoretical and technical problems have to be further studied and resolved.